Biopesticide formulations are generally designed based on customer needs and the physiochemical properties of the active ingredients, for example, the solubility of the active ingredient in water or non-aqueous solvents. There are two major categories of formulations, solid formulations and liquid formulations.
Solid formulations, such as water dispersible granule (WDG) and dispersible granules (DG), containing microbial active ingredients are seeing increased use today because of their relative safety compared to liquid formulations and the advantages they offer with regard to cost saving in packing and transportation, and the environmental benefits of eliminating the use of organic solvents. WDG formulations are designed to readily disperse on contact with the water carrier in a spray tank and provide equivalent performance to an emulsifiable concentrate product. DG formulations are normally designed for broadcast application without prior dilution in a carrier such as water. Granule products may be used for insect, weed, fungal pathogen and nematode control in both water and non-water applications. However, the microbial based granules are not typically readily to dissolve in water.
For example, Chromobacterium subtsugae strain PRAA4-1 (Grandevo®) is a gram-negative, violet-pigmented bacterium that was isolated from soil under an eastern hemlock (Tsuga Canadensis) in the Catoctin Mountain region of central Maryland. The United States Department of Agriculture found this isolate of Chromobacterium subtsugae to be orally toxic to Colorado potato beetle (Leptinotarsa decemlineata) larvae, live small hive beetle (Aethina tumida) larvae, southern corn rootworm (Diabrotica undecimpunctate) larvae and adults, and southern green stink bug (Nezara viridula) adults. Additional testing has shown that a Chromobacterium subtsugae strain PRAA4-1 treated diet resulted in reduced feeding in beet armyworm (Spodoptera exigua), cabbage looper (Trichoplusia ni), tobacco budworm (Heliothis virescens), diamondback moth (Plutella xylostella), and southern corn rootworm. Furthermore, this testing has suggested this microbe's insecticidal activity is due to reduction in weight or inhibition of feeding.
In another example, Bacillus amyloliquefaciens and Bacillus megaterium are gram-positive, spore-forming bacteria that were isolated from the soil. There is a large body of literature reporting the potential use of rhizosphere-associated bacteria in stimulating plant growth (Farah, Iqbel et al. 2008). These bacteria have plant growth promoting traits such as production of indoleactic acid, ammonia, hydrogen cyanide, siderophore, phosphate solubilization and antifungal activity.
Yet in another example, Pseudomonas fluorescens is a gram-negative bacterium that is found protecting the roots of plants from plant diseases. Previous work by the New York State Museum had isolated and identified a bacterial strain of Pseudomonas fluorescens (CL0145A) that can be applied as a dead cell mass—its highly selective biotoxin killed zebra mussels after three hours in one application but, unlike chlorine, did not kill any non-target species tested. Upon treatment, zebra mussels filter water treated with toxic CL0145A cell particles and pass those particles through their digestive system which gets destroyed.
Yet in another example, Burkholderia rinojensis isolate A396 is a gram-negative, straight rod bacterium that was isolated from the soil near the Rinoji Temple in Nikko, Japan by Marrone Bio Innovations. Contact and feeding bioassays reveal effective insecticidal and miticidal activities against beet armyworms (Spodoptera exigua) and two-spotted spider mites (Tetranychus urticae), respectively. Furthermore, these results suggest ingestion and contact as two mechanisms of action that cause larvae discoloration, stunted growth, molting issues, exoskeleton disintegration, and mortality.
Thus, there is a need to find formulations that can readily be dissolved in water.